class Solution {
    public int numIslands(char[][] grid) {
        int count = 0;
        for(int i = 0;i < grid.length;i++){
            for(int j = 0;j < grid[0].length;j++){
                if(grid[i][j] == '1'){
                    dfs(grid,i,j);
                    count++;
                }
            }
        }
        return count;
    }

    public void dfs(char[][]grid,int i,int j){
        if(i < 0 || j < 0 || i >= grid.length || j >= grid[0].length || grid[i][j] == '0') return;
        grid[i][j] = '0';
        dfs(grid,i,j+1);
        dfs(grid,i,j-1);
        dfs(grid,i-1,j);
        dfs(grid,i+1,j);
    }
}